<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <!-- <script>
        let arr = [1, 2, 3];
        //...arr;
        // 1, 2, 3

        function show(a, b, c) {
            alert(a);
            alert(b);
            alert(c);
        }

        // show(1, 2, 3);
        show(...arr);
    </script> -->

    <script>
        let arr1 = [1, 2, 3];
        let arr2 = [5, 6, 7];

        let arr = [...arr1, ...arr2];
        // let arr = [1, 2, 3, 5, 6, 7];

        alert(arr);
    </script>

</body>

</html>